Yersinia secretion apparatus (Ysa), the chromosomal type three secretion system (T3SS) is considered to contribute to virulence of high-pathogenicity Yersina enterocolitica biovar 1B. DNA‑sequence of Ysa pathogenicity island was determined for clinical isolate DM0110 of Y. enterocolitica 1B/O8 with origin in Poland. We found a premature stop-codon in the regulatory gene ysrR (mutation at position 269). Altered ysrR was detected in all tested 78 isolates of Y. enterocolitica 1B/O8 collected from clinical samples in Poland from 2004 to 2013. Since aberrations in YsrR are considered to inactivate Ysa, our findings may suggest Ysa is not indispensable for Y. enterocolitica 1B/O8 to infect humans.